Expansion control



Jan. 25, 1944. J, N. ROTH 2,339,815

EXPANS ION CONTROL Filed Oct. 17, 1940 2 Sheets-Sheet 1 Jan. 25, 1944. 1N R01-H EXPANSION CONTROL Filed Oct. 17, 1940 2 Sheets-Sheet 2 Patent-edJan. 25, 1944 i. u, .iixrnnslon CONTROL Joseph N. Roth, Balding, Mich.,4assigner, by mesne assignments, to Gibson Refrigerator Company,Greenville, Mich.. la. corporation of Michigan Application October 17.1940, Serial No. 361,629

9 Claims. (Cl. 62445) This invention relates to expansion control means,and more particularly to means for controlling the delivery of liquefiedammonia from a high-pressure portion of a continuous absorptionrefrigeration system to the evaporator of such a system.

One feature of this invention is that it provides improved means forcontrolling delivery of refrigerant from a high-pressure portion to alow-pressure portion of a refrigeration system; another feature of thisinvention is that it automatically controls the rate of flow ofrefrigerant to the evaporator in accordance with the rate at which therefrigerant is liquefied in the condenser, which latter rate can beconveniently controlled in accordance with refrigeration requirements;another feature of this invention is that it is particularly adapted foruse with a refrigerant having a high latent heat, as ammonia, and in acontinuousrefrigeration system', as a continuous absorptionrefrigerator; another feature of this invention is that complete controlof the delivery of refrigerant to the evaporator is had without the useof any moving parts, as in the conventional float-controlled expansionvalve; yet another feature of this invention is that the rate of flow ofrefrigerant through a capillary tube can be retarded more than would bethe case if such refrigerant passed through entirely in liquid form, andthis retarding effect can be varied in accordance with conditions in therefrigeration system; other features and advantages of this inventionwill be apparent from the following specification and the drawings, in

which:

Figure l is a schematic or diagrammatic showing of a system employingthis invention as embodied in a domestic continuous absorptionrefrigerator; Figure 2 is a detail view, principally in verticalsection, oi the expansion control arrangement; Figure 3 is a transversesectional view along the line 3--3 of Figure 2; Figure 4 is an endelevation of a. iilter element; Figure 5 is a sectional view along theline 5-5 of Figure 4; and Figure 6 is a view along the line 6-6 ofFigure 5.

In the particular embodiment of my invention described herewith, thesystem in general comprises a still adapted to have a mixture ofrefrigerant and absorbent, as ammonia and water, boiled therein by theapplication of heat; a condenser connected by a vapor conduit to thestill to liquefy the refrigerant vapor delivered thereby; an evaporatoror cooling unit in which the liqueed refrigerant is permitted tovaporize, the

.in Figure 1, the stm lodis adapted to contain a mixture of water andammonia. A nue Il is provided within the still and heat deliveredthereto by the combustion of gas or some other fuel delivered by theburner l2. An analyzer tower I3, in the form of a long cylindricaltubing enclosing the flue Il, rises from the upper part of the still,which is a vertical cylindrical vessel. Both the analyzer tower and thestill are provided with baille plates, as I4 and I5, these platesserving to stratify the liquid in the 'still and to improve theefficiency of the apparatus.

Rich ammonia vapors boiled off the liquor in the still pass upwardlythrough the analyzer tower I3 and then through the pipe connection I6 tothe rectifier I'l, a finned inclined tube at the top of the system. Fromthere the ammonia vapors. any entrained water vapor having been removedby the rectifier, pass down through the connection l8'to a condenser I9at the lower end of the apparatus. This condenser comprises one ormoreloops of piping, finned to increase the heat radiation. The ammoniavapor is here condensed into liquid ammonia, and then elevated by thevapor pressure behind it through the connection 20 to the receiver 2l.

The amount of ammonia boiled off and liquefied is a function of theconcentration of the liquor in the still and of the amount of heatsupplied to it, so that if the concentration of liquor is keptrelatively constant the rate of delivery of liquid ammonia to thereceiver 2l will be practically a direct function of the amount of heatsupplied to the still. The amount of fuel delivered to the burner I2,and thus the amount of heat supplied and the rate of delivery of liquidammonia to the receiver. can be regulated in any desired manner. as by avalve (not here shown) actuated in conventional manner by a thermostatin the cooling chamber of the refrigerator.

Liquid ammonia passes from the receiver 2| to the dry evaporator 22,preferably comprising several coils of piping, through the restrictioninterposed by control means which will hereafter be described in moredetail. The control arrangement is such that, as more liquid ammonia isdelivered to the receiver, flow from the receiver to the evaporator isincreased to maintain the level of liquid in the receiver within certaindesired limits.

Absorbing apparatus is provided in the form of an upper chamber orvessel 25 having extending downwardly therefrom a cooling and absorptionloop. This loop is formed by a pipe 26 extending down from the bottom ofthe absorber vessel; the absorber cooling coil 21, nned for better heatradiation; and the upwardly extending pipe or leg 28, terminating in thevessel 25 slightly above the level of absorption liquid therein.

Expanded ammonia vapor from the evaporator 22 first passes through asmall loop or coil 29, the purpose of which will be hereinafterexplained, then through the pipe 30 into the rising leg 28 of theabsorber loop, near the lower part thereof. The incoming vapor createsbubbles in the leg 28 of the absorber loop which provide a liquid liftor pump insuring circulation of absorption liquid through the loop.Inasmuch as the liquid in this rising leg is at all times the weakestliquor in the absorber, and cool as a result of passing through the coil21, all absorption takes place in the pipe 28 under normal conditions,the liquid flowing out of the top of this pipe being quite rich.

The level of liquid in the absorber vessel 25 is maintained by a float3l and valve 32 controlling delivery of weak liquor from the still. Thepipe 33 leads from the lower end of the still (where the liquor isweakest) through a heat exchanger 34 and then on up to open into theabsorber, the

flow into the absorber being controlled by the valve 32, which openswhenever the level of liquid in the vessel 25 drops below a desiredpoint.

The means for returning rich liquor from the absorber to the stillcomprises as its principal parts a transfer chamber 35, a valve assembly36, a pressure chamber 31 and associated operative interconnections. Aflow connection is provided from the leg 28 of the absorber loop, out ofthe short open-ended cross tube 28, through the jacket 38, pipe 39, andcheck valve 40, into the pressure chamber 31. When the valves are set ina certain position a flow path is provided from the pressure chamber,and thus from the absorber, through the pipe 4l, the valve mechanism,and the pipe 42 to the bottom of the transfer chamber 35, any vaportherein being vented through the .pipe 43 and the pipe 44(interconnected by the valve assembly) into the pressure chamber.

When the valve device is actuated, in accordance with a condition of thesystem, to move the valves to another position, the pipe 43 is connectedto the pipe 45 which is open to high pressure vapor in the pipe I8; andthe pipe 42 is connected to the pipe 46, connected through the heatexchanger 34 to a jacket 41 around a thermostat bulb in the still, andthen through a pipe 48 into the analyzer tower. The transfer chamber andconnecting pipes now being at high pressure, the rich liquor thereinflows into the analyzer tower and thence to the still until the valvesare again moved to the position first described above.

When the interconnection between the pressure chamber and the transferchamber is again provided there is, of course, a rush of high pressurevapor through the pipe 43 and 44 to the chamber 31. The check valve 40,however, prevents these vapors from getting back into the low pressureside of the system; and the liquid in the chamber 31, cooled by the coil29, rapidly absorbs the vapor, assisted in this respect by a fine streamof weak liquor bled into the chamber 31 through the conduit 49 branchingfrom the weak liquor pipe 33. The rapid absorption of rich ammonia vaporcauses the pressure in the chambers 35 and 31 to drop below the pressurein the absorber 25 for a brief time, so that there is a positivepressure-driven ow of rich liquor from the absorber to completely refillthe chambers 35 and 31. When these are completely filled with liquid theweak liquor entering through the branch pipe 49 immediately starts toraise the pressure therein, the check valve 40 closing; and shortly thechambers 35 and 31 will again stand at high pressure. There is thus onlya brief interval during which the valves in the assembly 36 mustwithstand the full difference of pressure between the high and low sidesof the system.

Actuation of the valve means in the valve assembly 36 is accomplished bya thermostat bulb 50 in the jacket 41 connected by a liquid actuatingleg 5l to a chamber in the bottom of the valve housing 52. Liquidrefrigerant in the pipe 46, open at all times to still pressure,generates a certain pressure within the Sylphon bellows 53; whereas thepressure of the actuating liquid in thethermostat bulb 50 (preferably apredetermined ammonia-water concentration) is effective against theexterior of the Sylphon 53. The valve arrangement preferably includes asnapaction mechanism, so that when the pressure of the thermostat liquidexceeds the still pressure by a certain amount the bellows, and thus thevalves moved by it, move to upper position; and when the bulb pressurehas dropped a certain amount below the still pressure the bellows andvalves move down to the other position. These two alternate positionseffect the connections heretofore described.

While the continuous absorption refrigeration system hereabove describedcontains a number of inventions and improvements over other knownsystems, these will not be described in more detail here, this presentapplication being particularly directed to improved means forcontrolling delivery of refrigerant from the high side to the low sideor evaporator of the system. Other improvements in the system are thesubject matter of my earlier filed joint and several copendingapplications, more particularly applications Serial No. 296,995, filedSeptember 28, 1939, Serial No. 298,110, filed October 5, 1939, SerialNo. 314,704, filed January 19, 1940, Serial No. 319,541, filed February1'1, 1940, Serial No. 326,292, filed March 27, 1940, and Serial No.352,328, filed August l2, 1940, and other later filed copendingapplications. The operation of the various other parts of the systemwill not, therefore, be described in further detail here; but theremainder of this specification will be directed to a description of theimproved expansion control apparatus, more particularly as embodied inthe apparatus shown in Figures 2 to 6.

Referring now more particularly to these latter figures, it will be seenthat the receiver 2l is in general a cylindrical vessel with its axishorizontal; and that the pipe 20, delivering liquefied refrigerant fromthe condenser I9, opens into a wall of the receiver near its upper part.For convenience of assembly and repair the pipe 29 is not weldeddirectly to the wall of the receiver 2 I, but to a plate 55; and this isbolted to a flange 56, as may be best seen in'Figure 3. It is irnportantthat the communication of the pipe 20 with the receiver 2| be near itsupper part, since in the operation of my improved control it isdesirable to maintain a quantity of liquified refrigerant in thereceiver at all times; yet it is desired to permit communication of thespace above this liquid with refrigerant vapor at condenser temperatureand pressure, so that no liquid trap should be provided in this part ofthe apparatus. In normal operation of a system of this kind refrigerantvapor partially liquefles in the condenser I9, and slugs of liquidammonia are pushed up the pipe 20 by the vapor. With the arrangementhere shown it is intended to have some liquid refrigerant at all timesin the receiver 2|; and some refrigerant vapor, at condenser pressureand approximately at condenser temperature, in the receiver above thisliquid.

Referring now more particularly to Figure 2, it will be seen that acapillary tube 51 provides connection between the receiver 2| and theevaporator pipes 22. This capillary tube is welded or otherwise sealedin an opening in a plate 58 separating the receiver from the evaporator;a small vportion of the capillary tube 51 extends straight out from thisplate to open into the evaporator pipe 22, but the major part of thecapillary tube is coiled up within the receiver 2|. The arrangement forconnecting the capillary tube to the evaporator tubing is the subjectmatter of my copending application Serial No. 501,936.. filed September1l, 1943. The other or righthand end of the capillary tube does not opendirectly into the main receiver chamber, but into a small auxiliarychamber 59 separated from the main receiver chamber by fllter means 60.This filter is similar in arrangement and operation to another filter 6|which is in the connection between the pipe 20 and the receiver 2|.

Referring now more particularly to Figures 4, and 6, it will be seenthat each of these filters comprises a main end plate 62 and a smallerend plate 63. These two end plates are separated by a, plurality ofwashers or filter elements, these being of two types and stackedalternately; and the whole assembly is held together by a bolt. The boltpreferably has a polygonal shank, as for example hexagonal, and thewashers are provided with similar holes so that when they are stackedupon the bolt shank they are nonrotatable thereon. As may be best seenin Figures 5 and 6, one of these types of washers, here identified as64, is a dise provided with six regularly spaced openings or holes 65.The other type of washer, here identified as 66, is a spider with legs61 projecting out between the openings in the other Washer. The endplate 62 is provided with openings, as 68, aligned with the openings 65in the one set of washers.

These washers are stamped out of sheet metal, as sheet steel, and areonly a few thousandths of an inch thick, always being of lesserthickness than the internal diameter of the capillary tube A with whichthey are to be used. Liquid passing tube are prevented from reaching itand clogging it.

Returning now more particularly to the arrangement shown in Figure 2, itwill be seen that a substantial part of the coiled portion of thecapillary tube 51 is immersed in liquid refrigerant, but a part of itstop is exposed to the warm refrigerant vapor. When liquid refrigerantenters a capillary tube its restriction to flow causes a pressure dropthrough the tube, so that as the liquid fiows therethrough its pressureat any given point decreases as it approaches the evaporator pipes.Under these conditions, because of the reduction in pressure, liquidrefrigerant in the capillary tube is colder than that in the receiver2|, its temperature progressively decreasing as it approaches the endplate 58. Under these conditions the exposed part of the coil acts as acondenser, part of the warm refrigerant vapor in contact with it givingup its heat and turning into liquid. This heat passes through the wallsof the capillary tube and in turn causes a change of state of the liquidrefrigerant therein, vaporizing or gasifying a part of it. Change ofstate retards flow of refrigerant through the capillary, since thechange not only creates back pressure in the tube, but also results in amuch greater volume of fluid therein, the gaseous refrigerant occupyingseveral times the space of the liquid refrigerant.

As the level of the liquid refrigerant in the receiver falls, more areaof the coil portion of the capillary tube 51 is exposed to therefrigerant vapor, and more gasification of liquid refrigerant.

in the tube takes place, thus providing more retardation of refrigerantflow therethrough. Similarly, if the level of liquid in the receiver 2|rises by reason of delivery of liquid thereto faster than it is passingthrough the capillary tube, there is less coil to be exposed torefrigerant vapor, and less retarding effect on refrigerant flow.Practically all heat input to the capillary tube comes from condensingaction where it is in contact with refrigerant vapor, the heatconduction of the liquid refrigerant being rather poor. It will thus beseen that if the receiver fills until the coils are completely submergedthe refrigerant will pass through the capillary tube substantiallyentirely in liquid state, so that there will be a greatly increased flowof refrigerant.

This automatic variation of heat input to the liquid within thecapillary tube, with its consequent variation of the retarding effect onthe fiow of refrigerant through the capillary tube, has proved veryimportant, particularly in continuous absorption refrigeration systems.Heretofore it has been necessary to use a float-actuated expansionvalve, yet the rate of refrigerant flow was so small and the pressuresso high that there was great wire drawing and frequent failure of theexpansion valve arrangement. The refrigeration art has heretoforethought it impossible to use a capillary tube to accomplish refrigerantcontrol under such conditions. In the first place, any attempts to use acapillary tube without the provision of some retarding means beyond itsordinary restriction to flow would require the use of such a fine tubeas to be impracticable; and secondly, the rate of refrigeration incontinuous absorption systems is controlled by varying the amount offuel burned, so that some means would have to be provided for enablinggreatly increased flow of refrigerant when the fuel input was high, anda greatly retarded ow of refrigerant to the evaporator when the burnerwas turned very low.

Turning first to the problem of the size of a capillary tube required ifused in the ordinary way in which it is used in electric refrigerators,it will be seen that the restriction of the capillary tube would have tobe in the neighborhood of twenty times as great as that imposed by acapillary used in a conventional electric refrigerator. In the firstplace, the latent heat of ammonia is so much greater than that of Freon,the common commercial refrigerant used in electrical systems, that itrequires about four cubic feet of Freon to equal to refrigerating effectof one cubic foot of ammonia. Moreover, the electric refrigerator isdesigned to pass a higher quantity of refrigerant than is necessary tohold the food chamber at a desired temperature, so that it may runintermittently and yet maintain an average evaporator temperature, forexample, of twelve degrees. Since the average electric refrigerator isso designed as to need to run only one-third to one-half the time, wecan assume that it is designed to pass to the evaporator about two andone-half times the amount of refrigerant which should be delivered in acontinuous machine. Moreover, where a capillary tube is used as a.control means, the rate of flow of refrigerant through the tube is afunction of the pressure differential between the high and low sides ofthe refrigeration system; and the average pressure differential betweenthe high and low sides of a continuous absorption machine is about twicethat between the high and low sides of an elec trically drivencompressor type machine. In a 95 E. room, for example, the condensingpressure of ammonia may be 181 pounds per square inch, with anevaporator pressure of eighteen pounds, a differential of 163 pounds;whereas the condensing pressure of Freon` may be 108 pounds as againstan evaporator pressure of 16 pounds, a differential of 92 pounds.

All of these differences are cumulative, so that the latent heat ratioof four to one, the rate of flow ratio of ltwo and one-half to one, andthe pressure differential ratio of about two to one should all bemultiplied. It is thus apparent that a capillary tube to be used tocontrol delivery of ammonia to the evaporator in a continuous absorptionrefrigerator should have about twenty times the restrictive effect of acapillary tube controlling delivery of Freon to the evaporator of anelectric refrigerator. While formulae have not as yet been developed forthe relations, it is known that lengthening a capillary tube, orreducing its internal diameter, increases its restrictive effect onfluid flow. In an electric refrigerator manufactured and sold by thecompany by which I am employed proper restrictive effect for Freon isobtained by the use of six feet of capillary tube having an internaldiameter of .032 inch. In order to greatly increase the restrictiveeffect in an attempt to control delivery of ammonia to the evaporator ofa continuous absorption refrigerator, I tried ten feet of capillary tubehaving an internal diameter of .0065 inch, and found it impracticable.In the first place, it did not provide sufficient restrictive effect tothe flow of refrigerant, blowing through at high room temperature; andin the second place, it was so undesirably small in internal diameterthat it plugged up with only small globules or droplets of oil.

By employing the improved arrangement which I have described above,supplying heat to the refrigerator through the capillary tube andcausing a change of state of some of it while i't is in the tube, I findthat sufficient restrictive effect is obtained by the use of three andone-third feet of capillary tube having an internal diameter of .012inch, about 35 inches of this tube being coiled up in the receiver.Moreover, the variation ln heat input to the tube with variation ofliquid level in the receiver causes the rate of delivery of refrigerantthrough the capillary tube to the evaporator to conform exactly to therate of delivery of liquied refrigerant to the receiver; and thisautomatic compensating action properly controls delivery throughexceedingly wide ranges of heat input to the generator. and through wideranges of temperature in the room in whicha domestic refrigeratorembocwing this invention operates.

While I have shown and described certain embodiments of my invention,itis to be understood that it is capable of many "modifications Changes,therefore, in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

I claim: I

1. Apparatus of the character described for controlling delivery ofliquefied ammonia from a high pressure portion to a low pressure portionof a continuous absorption refrigeration system. including: a receivingchamber in the high pressure portion; a capillary tube connecting thechamber to the low pressure portion to deliver refrigerant thereto, themajor portion of the capillary tube lying within the chamber and beingadapted to be at least partly immersed in liquid refrigerant therein,the construction and arrangement being such that the immersion varieswith the amount of liquid in the chamber and the part not immersed is incontact with warm refrigerant vapor.

2. Apparatus of the character described for controlling delivery ofliquefied ammonia from a high pressure portion to a low pressure portionof a continuous absorption refrigeration system, including: a receivingchamber in the high pressure portion in communication with thecondensing portion of the system through an opening in the wall of thechamber near its top; a capillary tube connecting the chamber to the lowpressure portion to deliver refrigerant thereto, the major portion ofthe capillary tube being coiled within the chamber and being adapted tobe at least partly immersed in liquid refrigerant therein, theconstruction and *arrangement being such that the immersion varies withthe amount of liquid in the chamber and the part not immersed is incontact with warm refrigerant vapor, whereby flow of refrigerant throughthe tube is automatically accelerated if the refrigerant is beingdelivered to the chamber more rapidly than it is passing through thetube.

3. Apparatus of the character claimed in claim 2. including a filter forpreventing blocking of the capillary tube.

4. A method for retarding flow of refrigerant through a capillary tubeproviding insufficient restriction to flow of liquid refrigerant,comprising exposing part of. said tube to gaseous refrigerant to deliverheat to said tube and gasify part of the liquid refrigerant thereinduring its passage therethrough, varying the amount of said tube exposedto said gaseous refrigerant in accordance with the amount of additionalretardation so desired, and delivering the refrigerant at a dischargepoint located substantially out of heat exchange relation with the partof said tube exposed to said gaseous refrigerant.

5. Apparatus of the character described for controlling delivery ofrefrigerant from a high pressure portion to a low pressure portion of arefrigeration system, including: a capillary tube through which therefrigerant flows; a receiving chamber in the high pressure portion intowhich one end of the tube opens; and means for delivering refrigerant tosaid chamber, the construction and arrangement being such that liquidand vapor separate in the chamber and heat is supplied to the tube fromthe vapor to gasify at least part of the liquid refrigerant therein andthe amount of heat supplied is increased when said rate of flow exceedsthe rate of delivery to said chamber and decreased when said rate of owis less than the rate of delivery to the chamber, the tube extending toa discharge end located substantially out of heat exchange relation withthe chamber.

6. Apparatus of the character described for controlling delivery ofrefrigerant from a high pressure portion to a low pressure portion of arefrigeration system, including: a capillary tube through which therefrigerant ows; a receiving chamber into which one end of the tubeopens;

and means for delivering liquid refrigerant and warm refrigerant vaporto the chamber, a substantial portion o f the tube lying within thechamber and adapted to be at least partly immersed in liquid refrigeranttherein, the construction and arrangement being such that the liquid andvapor separate in the chamber so that the immersion varies with theamount of liquid in the chamber and the part not immersed is in contactwith the warm Vapor to receive heat suiicient to gasify at least part ofthe liquid refrigerant therein, the other end of the tube being locatedsubstantially out of heat exchange relation with the chamber.

7. Apparatus of the character claimed in claim 5, wherein therefrigeration system is of the continuous absorption type and therefrigerant is ammonia.

8. Apparatus of the character claimed in claim 5, including a filter forpreventing blocking of the capillary tube.

9. Apparatus of the character claimed in claim 6, wherein therefrigeration system is of the continuous absorption type and therefrigerant is ammonia.

JOSEPH N. ROTH.

